Evaluation of helical magnetoelastic anisotropy in Fe-based amorphous wire from the decomposed susceptibility spectra

A novel method is introduced here to evaluate the intrinsic magnetic anisotropy from susceptibility spectra. The combination of two techniques namely, the decomposition of susceptibility spectra together with its dependence on applied torsion is employed to determine quantitatively the intrinsic helical anisotropy in an amorphous wire. The susceptibility spectra of Fe_77.5Si_7.5B₁₅ amorphous wires have been experimentally measured as a function of torsion. The reversible susceptibility is ascribed to wall motion of axial domains within the core, and to magnetization rotation within radial domains in the shell. The relaxation frequencies of these magnetization processes are evaluated to be 0.36 and 1.82 MHz, respectively. The static rotational susceptibility shows an asymmetric behavior with regards to positive and negative torsion angles, and is maximum at the torsion angle of 30 °, which counterbalances the internal stress. Present results indicate the existence of an intrinsic helical anisotropy corresponding to an average helical stress of 33 MPa.